Kinetics of oxidation of pinacol by aquocerium(IV) ions in aqueous perchlorate media

Abstract

The rapid oxidation of pinacol by Ce^IV_aq in aqueous perchlorate media has been followed using stopped-flow spectrophotometry. The oscilloscope traces and the kinetics show that the oxidation is inner-sphere, involving Ce⁴⁺(CH₃)₂COH˙(CH₃)₂COH_aq and Ce⁴⁺(CH₃)₂COH˙(CH₃),CO^–_aq in the rate-determining steps. This is compared with the oxidation of alcohols by Ce^IV_aq which involves analogous reactions and is similar to the inner-sphere oxidation of pinacol by Mn^III_aq in aqueous perchlorate media. Energies and entropies of activation are compared.